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18

The general principle is based on density. That is, less dense things will float on top of denser things. By analogy, imagine a human floating in a pool of water. Now imagine a human floating in a pool of saltwater- the human will float higher in the saltwater, since the density of the saltwater is higher. A hydrometer works similarly- it's just a ...


17

If brewing all-grain, taking gravity readings after mashing allows you to calculate your mash efficiency. If your efficiency is low (meaning you're not getting good conversion), you can use this knowledge to pin down problems in your recipe, milling, and mash/sparge processes. Measuring the gravity before and after fermentation allows you to calculate the ...


16

Refractometers are about the only other reasonable alternative for the homebrewer. They are a little more expensive, but usually much easier to use. They only need a few drops of wort/beer to get a good measurement. Take note however, reading final gravity of your beer is not a one step operation. You need to do a little more math if you want to ...


10

Refractometers can be used - they are a bit pricier, but on the other hand the sample you need is MUCH smaller. Here is a video on using one for brewing.


10

You certainly can. This is, for example, how you use a pycnometer. But, it's a bit of work. Two major problems: 1) You need to find a way to measure volume very, very precisely. The scales are reasonably accurate, but it is unlikely that you own a volumetric device accurate enough. Your SG will be screwed by an entire point for every 0.1% margin of error. ...


8

I don't re-introduce from the hydrometer vial, the four books I've read on homebrewing (Papazian, Miller etc...) suggest that you don't because this is a place where you can contaminate your beer. I doubt that there is a large risk because you've sanitized it all, but, I prefer to not take risks I only take a couple hydrometer readings so I don't lose that ...


8

Good Answer by Fishtoaster. The science is ancient, discovered by Archimedes. 1: Any object, wholly or partially immersed in a fluid, is buoyed up by a force equal to the weight of the fluid displaced by the object. In other words, if you put a ball, with volume 1 litre completely under water, there is an upwards force on the ball (buoyancy or flotation) ...


7

Yes. Specific gravity is calculated on relative densities (densitybeer / densitywater in the case of brewing). If you double the volume of the beer as you describe by diluting it with water, then the density will be half (roughly, not accounting for intermolecular interactions). (Dbeer / 2)/ Dwater = (Dbeer / Dwater) /2, so multiplying by 2 would restore the ...


6

Never return beer to the fermentor. Its not worth the risk of contaminating the whole batch. That is your sample to read, check for color and clarity and more importantly taste. I think its sort of tough to read the hydrometer in the bucket, especially if you have to compete with floaties in the bucket too. I'd use some siphon tubing and pull a sample ...


6

You can try filling the tube up to (or at least close to) the top, so that when you lower the hydrometer, most of the foam spills over the edge. Once it's that high up, it's not too hard to blow most of the remaining foam off. Don't forget though to give the hydro a dunk and spin to dislodge any bubbles stuck to the bottom of the hydrometer from an ...


6

Your process sounds fine - it's the way you're using the hydrometer that's the problem. To estimate alcohol content, you need to take a reading at the start of fermentation. You cannot read the alcohol content from the hydrometer alcohol scale at the end of fermentation. The hydrometer cannot measure the alcohol content directly, but it can estimate how ...


6

You are absolutely correct. Unless something is dissolved into the liquid, or there's so much trub that the hydrometer is sitting on top of it, the reading will be unaffected.


5

I have brewed many batches where I never checked the gravity in the past. You don't really need to check the gravities to make great beer. You do run the risk of not knowing when a beer is complete and maybe having overcarbonation issues in the bottle. But good fermentation practices should, normally, take care of that. However, I think that when you get ...


5

It might be Brix or Plato, which are basically the same. To test, mix up a 10% solution of sugar: 10 grams sugar in 90 grams water. If the scale is Brix, your solution should read 10 at the calibration temperature. If the units are gravity points, it will read 40.


4

Obligatory Disclaimer: Though I do have some formal education, I am by no means a professional chemist, so please take my answer for what it is - semi-educated speculation. As you hinted, back titration is a popular method of determining alcohol content in alcoholic beverages, especially wine. It would make sense that a similar approach could be used for ...


4

You've covered the two main likely causes, with stratification being the most significant cause of error. Another potential error is in the volume measurement - if this is out, then all the calculations to relate pre and post boil gravity will be out also. Related to that is the 4 percent shrinkage that happens as wort is chilled from boiling to pitching ...


4

Just add the difference. The error is probably due to the paper scale shifting. To get a non-linear error, the diameter of the stem would have to have changed. Also, you should add the error back before you make any temperature correction (although it likely won't make much difference).


4

Before doing any math whatsoever, be sure to check the packaging for the specific hydrometer you are using. When mine broke recently, I went back to my LHBS and purchased a replacement (same store, same shelf, same brand) not only does it have different directions (above vs below meniscus) but it also has a different calibration temperature. Once you're ...


4

EDIT: I'm not sure I realized it was 50 points we were talking about here, or just let my attention wander for a bit! Suspended solids can make a difference (see the comments), but you'd almost have to be measuring the SG of slurry for it to make that much of a difference! If the original recipe called for 2 cans of extract, and you used 3 then that's just ...


4

Here's a different approach to answering your question. Another completely valid, and backwards way of asking your question would be to ask: "How did people know that a hydrometer was an indicator of the beer being done?" The hydrometer really doesn't tell you that your beer is "done". What it tells you is that the sugars have been converted by yeast into ...


3

While @tallie's overflow answer is excellent, you can also just wait. I take my sample into a footed hydrometer test jar. Set it aside and do other brewery things while the foam settles.


3

Since this is secondary your gravity shouldn't be changing much. Unless you're moving to secondary during active fermentation, your beer should be at final gravity when you move it. Unless you're adding fermentables to your secondary, I can't think of a reason to track gravity. And if you are adding fermentables, then you might have some kreusen. And that ...


3

The only other thing I can think of that isn't in mdma's answer is that your hydrometer is miscalbirated. Check that it reads 1.000 in distilled water at the temperature that the hydrometer is calibrated at.


3

If the trub is actually physically holding the hydrometer up, preventing it from moving down, then unambiguously: yes, the trub will render your hydrometer reading useless. If, on the other hand, the trub is suspended in the liquid, it is a mixed bag. Suspended solids will impact a hydrometer reading, but for brewers it is usually very minimal. The only ...


2

I'd leave it be in the carboy as is. Racking again and again increased your chance of infecting it with wild microbes. Let it continue for another week and check the reading again. Bubbling in teh airlock is never a good indication of whether something is done or not. Its all about the hydrometer. I'd put your hydrometer in some water and just look at ...


2

I too have broken so many hydrometers. My current strategy is to just be super careful with it. We treat it like a VIP now and haven't broke one in the last year or so. Use and put it away ASAP. However, now I'm interested in refractometers. Never knew they existed.


2

There's definitely a thermal shock issue, and you shouldn't place a hydrometer into any hot liquid … but I don't think that's what you're getting at. I, too, imagine the hydrometer temperature correction factors will break down after some point, but I can't respond to where that point is; I'd not go past 90°F. Before I got a refractometer, I would have a ...


2

It looks like the alternative to lead weights in the bottom of a hydrometer is steel shot. You should be able to check the difference between the two with a magnet. Alternatively, if you have a blowtorch, lead has a far lower melting point than steel. Just be very careful of molten metal. I'd also suggest in the future taking a sample of wort and cooling ...


2

There is absolutely no way to guess a recipe's OG without knowing the particulars of the recipe. Likewise, suspended solids won't affect the reading by a significant margin unless they are actually bound to the hydrometer itself. There are several things that could effect a hydro reading. Did you add top-off water before you took the reading. If so, ...


2

Assuming you're talking about weighing a small sample of a known, accurate volume, it seems like you'd be able to get a ballpark idea about the SG using that method. I have no idea what the margin of error would be though. Presumably you'd need to take temperature into account as you do when using a hydromenter and possibly the amount of alcohol. For the ...



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